Turbine blade lock



P 1961 R. w. GUERNSEY EIAL 3,001,760

TURBINE BLADE LOCK 2 Sheets-Sheet 1 Filed Aug. 7, 1959 w m m w P 1961 R. w. GUERNSEY ETAL 3,001,760

TURBINE BLADE LOCK 2 Sheets-Sheet 2 Filed Aug. 7, 1959 ,1 Jam/21M; Z2

ATTORNEY United States Patent 3,001,760 TURBINE BLADE LOCK Robert W. Guernsey, George W. Mason, and Earle R.

Wall, Jr., Indianapolis, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 7, 1959, Ser. No. 832,256 1 Claim. (Cl. 253-77) The present invention relates to an improved type of locking device for retaining a turbine blade member against axial movement relative to the turbine wheel on which it is mounted.

It is common practice in constructing a turbine wheel to provide a base or wheel member having a plurality of axially extending peripheral recesses formed in the wheel and within which recesses the individual turbine blades are adapted to be mounted. In cross section the turbine wheel recesses have the appearance of an inverted Christmas tree or more properly a tapered dovetail construction with which a similarly shaped base on the turbine blades coacts to retain the turbine blades against radial movement relative to the turbine wheel. With this standard type turbine wheel assembly, it has also been the practice to utilize pin members to lock the turbine blades against axial movement relative to the wheel. Such pins have been relatively unsatisfactory from several points of view. First of all, in utilizing such turbine pin locks it is necessary to drill holes through both the turbine wheel rim adjacent the dovetatil recesses as well as providing a corresponding hole in the base of each turbine blade member. There has been a high rejection rate of the turbine wheels with this type of turbine blade lock device due to cracks or fractures which have developed around the pin holes. In addition, once the pins have been inserted and the turbine wheels operated for a period of time, corrosion around the pin and pin holes has made the removal of the pin and the disassembly of the turbine wheels very diflicult.

The present invention relates to a new and improved turbine blade lock device which substantially eliminates turbine wheel rejections due to failures caused by providing a seat for the turbine blade locks. In addition, the subject blade lock device is very simply disengaged permitting ready disassembly of the turbine wheel.

More specifically, the subject turbine lock device includes a spring clip type member which is adapted to be disposed within a small recess formed in the turbine wheel rim intermediate adjacent dovetail recesses and which clip includes a radially extending portion adapted to coact with a correspondingly shaped notch formed in one edge of the turbine blade base.

The details as well as other objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

In the drawings:

FIGURE 1 is a partially sectioned portion of a turbine wheel embodying the present invention;

FIGURE 2 is a view along line 22 of FIGURE 1;

FIGURE 3 is a plan view showing a pair of adjacent turbine blades removed from the wheel;

FIGURE 4 is a perspective view of the preferred form of locking clip; and

FIGURES 5-7 are modified forms of locking clips.

Referring to FIGURE 1, a turbine wheel is shown at It) and includes a rim portion 12. A plurality of axially extending tapered dovetailed recesses 14 are formed in the periphery of wheel rim 12. Each recess 14 is adapted to receive the correspondingly shaped base or platform portion 16 of a turbine blade 18. Each turbine blade or bucket member 18 is attached to the wheel rim by axially sliding the member into one of the peripheral Patented Sept. 26, 19 61 recesses 14. The dovetail construction of the recesses and turbine bucket platforms retains the buckets against radial movement relative to the wheel under the considerable centrifugal forces that are developed as the rotor assembly rotates. This is typical turbine rotor construction and does not, per se, constitute a part of the present invention.

It has been the practice in the past to drill a hole through the thinnest portion 20 of the wheel rim and to provide a corresponding hole in the turbine blade platform to permit a pin member to be inserted through the wheel rim and into engagement with the bucket platform and in this way to retain the bucket against axial movement relative the wheel rim. As already noted, this type of turbine blade lock construction has been unsatisfactory due to wheel rim fractures developing about the holes as well as the difiiculty experienced in removing the buckets after the rotor has been in use.

In the present invention, as best seen in FIGURES 1 and 3, a recess 22 is formed in the periphery of each of the wheel rim portions 24 intermediate adjacent wheel rim recesses 14. In general, recesses 22 are of a rectangular shape. A corresponding notch 26 is formed in each turbine bucket platform so as to be adjacently aligned with the corresponding turbine wheel recesses 22 when the buckets are in proper axial position on wheel rim 12.

A spring clip type locking member 28, as best seen in FIGURE 4, is adapted to be disposed within each wheel rim recess 22. Spring locking clips 28 are made from a suitable temperature and corrosion resistant strip steel stock. Each clip includes a base portion 30 having a substantially hat portion adapted to seat within the wheel rim recess 22, a short curved end portion 32 and a longer end portion which terminates in a flat tongue or tab 34. From the construction of clip 28 it is apparent that the latter will be capable of flexing for the purpose to be better understood subsequently.

Referring to FIGURES 1 and 2, it will be seen that the clip member is positioned within the turbine wheel recess 22 such that the clip tongue 34 is disposed within the turbine bucket notch 26. Since turbine rim recess 22, clip 28 and turbine bucket notch 26 are of substantially the same length it is apparent that with the clip in position, as shown in FIGURES 1 and 2, that the buckets will be restrained against axial movement.

To assemble the turbine buckets 18 upon the turbine wheel rim, each clip 28 is disposed within arim recess 22 at which time, through a suitable tool such as a screwdriver, the clip tongue 34 is flexed into the space between adjacent bucket platforms permitting a turbine bucket to be axially moved into position within a dovetailed recess 14 until the bucket is in proper axial position at which time the platform notch 26 and wheel rim recess 22 are aligned. Whenthe alignment has taken place the clip tongue is released and allowed to flex into the platform notch locking the bucket in position. The short curved section 32 of clip 28 is disposed in subadjacently abutting relation to the overhanging platform portion 35 of the turbine bucket adjacent the one being locked by the clip. This provides support for the clip and prevents possible undesired movement thereof.

Overhanging platform portions 35 of adjacent turbine buckets terminate to provide a space 37 slightly wider than the thickness of clip 28 so as to permit proper assembly and disassembly of the buckets on rim 12.

The turbine rotor buckets may be removed from the wheel by simply reversing the process which includes engaging the clip tongue with a suitable tool, moving the same out of the appropriate bucket platform notch and thereafter sliding the bucket axially oif the wheel rim.

As seen in FIGURE 6, it is possible to construct a on the wheel.

4 e 4 a clip member 36 so as to have a pair of tongues 38 and 40 permitting the locking of adjacent buckets.

It is apparent that various structural modifications may he mad i v t ect Spring q nwa fi n the o e the sh n vi he Pe sant semena addition to the one of'FI GURE "6, other possible neditications of spring clip construction are shown in FIG- U R ES 5 and 7. Clip 41 of themodificationof FIGURE 5' i ta a l the m s he amm n a FIG- URE 4. In both the modifications of FIGQBES and 6,, as well as that of FIGURE 4, the tongue portion of these clips which coact with the bucket platforinnotches are engaged by a suitable tool and moved circumferensa l t Pe mi s b y and q s 'se fl h r Of he wa However, the modification ofJFIG- 7 the locking portion or tongue 42 of clip 74- would be engaged by a suitable tool depressed radially e ative t t Wheel to new? srhias ba k a em r. and i s bl We claim:

A turbine o a sembl amntisis heel m m: her having a rim, a plurality'of circun ferential1ysad tapered dovetailed recesses f orinedin said rirnl'sa id reextending axially of said wheel s a ing into the periphery of said rirn a plurality of turbine buckets adapted to he supported within said recesses, each of said buckets including a platforni having a tapered dovetailed cross'section corresponding to the crosssection of said wheel rim recesses, saidfrecesses andpl atforn coacting to retain the turbine buckets against radial more; rnent relative to said wheel a second set of .rec wses formed in the periphery of saidrirnintermediate the turbine bucket receiving recesses, each platforrn includsomeoing portions overhanging snbadjacent second set recesses,

' saidsecond set of recesses having circumferentially extending opposed shoulders, a notch formed in each bucket platform, said notch being of substantially the samelength as the second set of recesses and adapted to be aligned therewith When'the turbine bucket is in the proper axial position on said rim; and a spring clip nien ber disposed in each of said second recesses, each of said clips being of substantially the same length as the platform notch and being disposed between said recess shonlders, said clip including a substantially fiat base'po'rtion adapted to seat within one of the second recesses, a short curved section extending from oneend of the base portion and another ciirvedsection extending from the other end of the base portion, said other curvedisection terminating in a tongue portion adapted to engage said bucket platform notch, said short curved seotion'and said other curved section ofthe clipbein'gdisposed in subadjacently a utting relation respectively with the overhanging portions of adjacent turbine blade platfornis. Y

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